Preparation method of anode material lithium iron (II) phosphate for lithium ion cell

Abstract

The invention discloses a preparation method of anode material lithium iron (II) phosphate for a lithium ion cell. The preparation method mainly comprises the following two steps: (1) synthesis of precursor Li3Fe2(PO4)3, blending a lithium source, an iron source and a phosphorus source according to that the molar ratio of Li to Fe to P is 3:2:3, taking deionized water, absolute ethanol or acetone as a medium, ball-milling for 0.5-24 h, drying the obtained slurry, thermally treating for 3-24 hours at the temperature of 500-900 DEG C to obtain the precursor Li3Fe2(PO4)3; and (2) blending the obtained precursor Li3Fe2(PO4)3 and iron powder according to the molar ratio of 1:1, taking deionized water, absolute ethanol or acetone as the medium, ball-milling for 0.5-24 h, drying the obtained slurry, placing the dried slurry into a high-temperature furnace, under the atmosphere of inoxidizability, baking the dried slurry for 5-24 h at the temperature of 500-800 DEG C, and at last preparing the lithium iron (II) phosphate material. By adopting the principle that the lithium iron (II) phosphate material is synthesized by oxidation reduction between zero-valent iron and ferric iron source Li3Fe2(PO4)3 at high temperature, firstly, the pure phase Li3Fe2(PO4)3 intermediate is synthesized in advance, and then reacted with the zero-valent iron to synthesize the lithium iron (II) phosphate, so that the reaction process is easy to control. The synthesized product Li3Fe2(PO4)3 is high in chemical purity, good in electrochemical performance and high in batch stability.

Description

Technical field [0001] The invention belongs to the technical field of energy materials, and relates to a method for preparing lithium iron phosphate, a positive electrode material for lithium ion batteries. Background technique [0002] Lithium-ion batteries have the characteristics of high energy density, long cycle life, low self-discharge, no memory effect, and environmental friendliness. Small lithium-ion batteries have occupied a monopoly position in information terminal products (mobile phones, portable computers, digital cameras) At present, its application fields have expanded from mobile phones and notebooks to power tools, light electric vehicles, hybrid electric vehicles, telecommunications backup power, space and aerospace and other fields, with broad application prospects. [0003] LiFePO 4 It is currently one of the more concerned lithium-ion battery cathode materials. It has the characteristics of high thermal stability, long cycle life, cheap and abundant raw mater...

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Problems solved by technology

Literature (Feng Yu, Jingjie Zhanga, Reaction mechanism and electrochemical performance of LiFePO 4 / C cathode materials synthesized by carbothermal method[J].Electrochimica Acta.2009) The analysis of the reaction process during the synthesis of lithium iron phosphate materials also proves this point. Due to the existence of side reactions or competing reactions, the synthesis of phosphite The reaction process is difficult to control when the iron lithium material is used, the batch stability is poor, and the product has impurities or miscellaneous phases, which reduces the electrochemical performance of the material

[0008] PCT / US / 9706671 discloses Li 3 Fe 2 (PO 4 ) 3 It is a lithium intercalation compound, but its discharge platform is lower (2.8v vs Li + / Li), the specific capacity is about 100-120mAh / g, which is difficult to be practically applied in secondary lithium-ion batteries with high specific energy requirements

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